1. Even if the number is blocked by service provider, they'll get a text that your number tried to call them2. If it's a handset feature then the short ring you hear before getting cut off will give them a missed call3. If the receiving number is set to divert all calls or if unanswered or if busy to voicemail and your calls are leading to voice mail then your number isn't blocked UNLESS the receiver's service provider / handset allows a feature to divert all calls from a particular number to voice mail / alternate number :)